org.apache.cassandra.utils.MergeIterator.Candidate - has Comparator field which is the same for all Candidates under an MergeIterator instance, we can move the field to MergeIterator level. Candidate is 4.8% of all allocations and we can save 20% (~1% of all allocations) of it for JDK 21 with compressed references on.
switch from ArrayList to array in org.apache.cassandra.db.rows.Row.Merger
The ArrayList iterator costs 0.72% and BulkIterator.Adapter costs 0.35%. So, in total we can save here ~1% of total allocations.
patch by Dmitry Konstantinov; reviewed by Francisco Guerrero for CASSANDRA-21359
Set 1 thread and 1 second for the measurement iteration (note: it is a smoke test only, we do not analyze results from such short measurements)
Exclude some options for heavy benchmarks by default
Shutdown all threads once JMH test is completed to avoid awaiting of a forked JVM till timeout at the end
patch by Dmitry Konstantinov; reviewed by Michael Semb Wever for CASSANDRA-21388
- now() functions must be deterministic (and derived from Accord timestamp)
- tombstone GC and TTL evaluation must be deterministic and based on both Accord timestamp and Accord GC mechanisms (that guarantee completeness of execution)
patch by Benedict; reviewed by Alex Petrov and Ariel Weisberg for CASSANDRA-21376
- consumer and producer threads wait signal without acquiring the lock first
- lock owners may prepare more work than they need, moving some dynamically-adjusted portion of the work from the prioritised lock-managed structures onto a non-blocking queue, so that other threads may consume work from there; the portion is continually micro-adjusted to target some available work whenever the lock is acquired.
- adopts/supports some features of the SEPExecutor:
- threads may auto-adjust the number of running threads based on how much time is collectively spent waiting, to minimise time spent signalling
- consumers may (timed-sleep) poll rather than await a signal, reducing the number of kernel interactions needed; relying on the auto-adjustment to bound the time the scheduler spends waking threads with no work to do
Also Fix:
- Client Result should not be persisted or included in Command object at any time
patch by Benedict; reviewed by Alex Petrov and Ariel Weisberg for CASSANDRA-21375
The following subcommands have been added:
* abortbootstrap Cancel and undo an inflight bootstrap
* abortmove Cancel and undo an inflight token move
* abortdecommission Cancel and undo an inflight decommission
* assassinate Remove a node from cluster metadata
* resetcms Redefine the CMS membership
* move Modify a node's (single) owned token
* describe Output a summary of the cluster metadata
* forcejoin Force a registered or joining node into a JOINED state
* print Output a full rendering of cluster metadata
* printdirectory Output a full rendering of the directory
* printdataplacements Output the full data placements
Patch by Venkata Harikrishna Nukala; reviewed by Alex Petrov and Sam Tunnicliffe
for CASSANDRA-19151
Follow-up to the trunk PR #4807 forward-merge for cassandra-5.0. The
trunk R1 commit (8e0700a7cb on the chain leading to 32826fe563)
rewrote reference/cql-commands/commands-toc.adoc to retarget 38
broken xref:reference/cql-commands/<page>.adoc[...] entries to the
corresponding anchors in developing/cql/{ddl,dml,functions,mvs,
security,types}.adoc, kept 6 entries that still resolve under
cassandra:reference/cql-commands/, and dropped 4 DSE-only entries
(RESTRICT, RESTRICT ROWS, UNRESTRICT, UNRESTRICT ROWS).
The same transformation is applied here to cassandra-5.0. The trunk
commit was not cherry-pickable because 5.0's commands-toc.adoc had
diverged from trunk's pre-R1 version by ~9 lines (the DSE-only
entries plus an unrelated formatting drift); a direct edit replacing
the file with trunk's post-R1 content was the cleanest application.
One trunk-only entry is omitted: LIST SUPERUSERS (target
developing/cql/security.adoc#list-superusers-statement). That anchor
does not exist on cassandra-5.0; the LIST SUPERUSERS command was
added after 5.0.
All 29 retarget anchors plus the 6 cassandra:reference/cql-commands/
target pages verified to exist on upstream/cassandra-5.0.
patch by Patrick McFadin; reviewed by TBD for CASSANDRA-21342
Forward-merge of the trunk fix (commit 32826fe563) to cassandra-5.0.
Restricted to the changes whose broken-target patterns exist on this
branch.
Two trunk commits intentionally omitted:
- P1 (memtable.adoc retarget): the memtable sections containing the
broken xref were added on trunk only and do not exist on 5.0.
- R1 (commands-toc.adoc rewrite): commands-toc.adoc on 5.0 diverges
from trunk by ~9 lines; the 38-row retarget mapping will be applied
as a separate follow-up commit on this branch.
patch by Patrick McFadin; reviewed by TBD for CASSANDRA-21342
Resolve broken cross-module xrefs and image/anchor targets across the
cassandra docs tree. Companion to apache/cassandra-website#319 (merged
2026-05-13) under the same JIRA umbrella.
patch by Patrick McFadin; reviewed by Brandon Williams for CASSANDRA-21342
- TransactionStatement token aware routing
- Mitigate convoy effect:
- ExecuteTxnBacklog v1 can execute single key transaction backlogs and disseminate the result
- Direct local execution possible for single key transactions
- Use shardAppliedBefore instead of gcBefore to cleanup CFK faster
Also Improve:
- Introduce distributed tracing
- Combine RejectBefore and MaxConflicts
- Self-addressed messages are delivered directly
- Disable AccordSyncPropagator by default, as incompatible with large clusters
- FastPathStrategy.SIMPLE should not modify fast path contents; FastPathStrategy.UP introduced to adopt this behaviour
- Configurable queue prioritisation
- ProtocolModifiers mostly final
- Remove unnecessary condition check when serializing TxnUpdate
Also Fix:
- SequentialExecutor ownership bug
- BTree.XUpdater.reset()
patch by Benedict; reviewed by Alex Petrov and Ariel Weisberg for CASSANDRA-21361
use compression ratio to scale the amount of remaining disk usage
CompactionInfo::estimatedRemainingWriteBytes is uncompressed, causing compaction to be rejected due to size when it has space to complete
patch by Matt Byrd; reviewed by Dmitry Konstantinov, Marcus Eriksson for CASSANDRA-21245
Co-authored-by: Jon Meredith <jmeredithco@apple.com>
- Clean Shutdown/Restart
- Rebootstrap to allow nodes to rejoin consensus if they are out of sync, or did not shutdown cleanly
Improve:
- Improve efficiency of BTreeReducingRangeMap
- DurableBefore backed by BTreeReducingRangeMap
- Soft reject new transactions when a replica has a backlog of work
- system_accord_debug.command_store_ops supports starting journal replay
Fix:
- Ensure SequentialExecutor.owner is unset only by the owner
- Detect and avoid taking two AccordExecutor locks simultaneously
- MaxConflicts serializer
- tryToExecuteListening after replay, to handle invalidated dependencies
- TxnNamedRead does not close a RowIterator, leading to native memory leaks
- GetLatestDepsNack serialization
- journal.readLast() did not read last
- DefaultRemoteListeners not correctly synchronised
- RangeTxnScanner cancellation assumes was already started
- Start cfk compaction before replay
- txn_graph should avoid visiting parents twice (possible if two different dependency chains connecting them in the graph)
- Topology.cloneEquivalentWithEpoch should also share nodeLookup and ranges, especially to accelerate computeWaitForEpoch/computeScope
- Do not invoke slowReplicaDelay or slowCoordinatorDelay during restore
- Do not fail if slowReplicaDelay or slowCoordinatorDelay are invoked without knowing the transaction
patch by Benedict; reviewed by Alex Petrov and Ariel Weisberg for CASSANDRA-21355
SinglePartitionReadCommand.Group#create - typical single partition select, use singletonList instead of ArrayList + Object[]
SelectStatement#getSliceCommands - remove unnessesary cloning of partition key, it is a part of a very old patch, now we copy all values from Netty buffers
SelectStatement#getSliceCommands - typical single partition select, use singletonList instead of ArrayList + Object[]
SinglePartitionReadQuery.Group#maybeValidateIndex, avoid iterators for restrictionSet if a full partition is selected
patch by Dmitry Konstantinov; reviewed by Francisco Guerrero, Stefan Miklosovic for CASSANDRA-21351
Dmitry Konstantinov